This was one of the "I will get around to it" projects and I just got around to it.
Lots of tool height setters out there but not many allow you to measure the height so you can set the
tool a specific amount lower than center. The micrometer is set in place with it's set screw and set to a reading
on the barrel like 150 thou. If your bit was exactly on center height then 150 is now calibrated to your lathe center.
If you want to measure the difference of another tool just read the amount from 150 and you will know the difference.
Handy if you are not using a QCTP and need to put in a shim under your tool bit. Now you know exactly how thick
that shim needs to be to get you on center.